Cool another KM instructor!
Towel pull ups are a good sub for the rope climb. From the FAQ page:

The "official" CrossFit Warm-up is in the April 2003 CrossFit Journal.

3 rounds of 10-15 reps of
Samson Stretch (do the Samson Stretch once each round for 15-30 seconds)
Overhead Squat with broomstick
Sit-up
Back-extension
Pull-up
Dip
Note that for a workout that's dip or pullup-centric, you might want to do something else in the warmup.